The present invention relates to methods and devices for treating multiple interval well bores and more particularly, the use of an isolation assembly to provide zonal isolation to allow selected treatment of productive or previously producing intervals in multiple interval well bores.
Oil and gas wells often produce hydrocarbons from more than one subterranean zone or well bore interval. Occasionally, it is desired to treat or retreat one or more intervals of a well bore. Reasons for treating or retreating intervals of a well bore include the need to stimulate or restimulate an interval as a result of declining productivity during the life of the well. Examples of stimulation treatments include fracturing treatments and acid stimulation. Other treating operations include conformance treatments, sand control treatments, blocking or isolating intervals, consolidating treatments, sealing treatments, or any combination thereof.
One difficulty in treating a selected interval of an already producing well bore is the lack of zonal isolation between intervals. That is, each of the selected intervals to be treated may be in fluid communication with other intervals of the well bore. This lack of isolation between intervals can prevent targeted treatments to selected intervals because treatments intended for one selected interval may inadvertently flow into a nonintended interval. Thus, before treating or retreating a selected interval of a well bore, the selected interval will often be isolated from the other intervals of the well bore. In this way, treatments may be targeted to specific intervals.
Conventional methods for reisolation of well bore intervals include the use of isolation devices such as, for example, straddle packers, packers with sand plugs, packers with bridge plugs, isolation via cementing, and combinations thereof. Such conventional methods, however, can suffer from a number of disadvantages including lower rate throughputs due to additional well bore restrictions inherent in such methods, poor isolation between intervals, and depletion between intervals.
Thus, a need exists for an improved method for providing isolation between well bore intervals to allow treatment or retreatment of selected intervals in multiple interval well bores.